332
D. J. BELL
Taking the physiological point of view, di- and higher saccharides
which are found in biological environments can be classified into four
main groups. First we have those reducing substances that are found
only in relatively small amounts because they occur as dynamic intermediaries in some anabolic or catabolic system such as starch-glucose
from which maltose (G\/4G) and maltotriose (G\/4G\/4G) can
be sometimes isolated. Secondly we find reducing oligosaccharides in
nonreducing glycosidic combination with noncarbohydrate radicals
(aglycones) (203) from which they may be liberated, with the intersugar links intact, by an appropriate hydrolytic procedure which may
take place in the natural environment. An example is the disaccharide
primeverose (X /\ 6G) which occurs naturally in glycosidic combination
with alizarin as "ruberythric acid" (X /\ 6G—"alizarinyl"). Thirdly we
have the unique group of reducing sugars which are excreted from the
mammary glands of female mammals and comprises lactose (Ga /\ 4G)
with smaller amounts of reducing tri-, tetra-, penta-, and hexasaccharides
built up by attachment of various sugar units to lactose itself. These
sugars do not appear to undergo any changes in the milk. As will be
noted later, lactose, so commonly regarded as a sugar unique to the
female mammal, is also to be found in the vegetable kingdom. Fourthly,
we have the two widely distributed nonreducing disaccharides sucrose
(G/\/Ff) and trehalose (G\/\/G) which seem to be forms in which
potential energy can be transported or stored in a readily available form
in the sap or body fluids of many organisms. In addition, it has become
clear that sucrose molecules, and possiblv trehalose as well, form
"anchors" on to which may be attached considerable numbers of other
sugar units, usually in chains, to generate higher oligo- and polysaccharides. The fructosans of the inulin and levan types can often be shown
directly or indirectly to contain a moiety having the sucrose structure
(see Chapter 8).
The nonreducing disaccharides and their homologs will be considered first.
A. NONREDUCING OLIGOSACCHARIDES
1. aa-Trehalose
This sugar (XCII) has been known for a very long time; it was
first obtained from ergot in 1832 (204) but got its name from trehala
manna (of insect origin) from which it was isolated in 1859 (205). A
full historical account of early work on trehalose has been published
(206). The sugar occurs in a wide variety of situations, in fungi, freshwater algae, lichens, a pteridophyte (Selaginella lepidophylh), yeasts,
D. J. BELL
Taking the physiological point of view, di- and higher saccharides
which are found in biological environments can be classified into four
main groups. First we have those reducing substances that are found
only in relatively small amounts because they occur as dynamic intermediaries in some anabolic or catabolic system such as starch-glucose
from which maltose (G\/4G) and maltotriose (G\/4G\/4G) can
be sometimes isolated. Secondly we find reducing oligosaccharides in
nonreducing glycosidic combination with noncarbohydrate radicals
(aglycones) (203) from which they may be liberated, with the intersugar links intact, by an appropriate hydrolytic procedure which may
take place in the natural environment. An example is the disaccharide
primeverose (X /\ 6G) which occurs naturally in glycosidic combination
with alizarin as "ruberythric acid" (X /\ 6G—"alizarinyl"). Thirdly we
have the unique group of reducing sugars which are excreted from the
mammary glands of female mammals and comprises lactose (Ga /\ 4G)
with smaller amounts of reducing tri-, tetra-, penta-, and hexasaccharides
built up by attachment of various sugar units to lactose itself. These
sugars do not appear to undergo any changes in the milk. As will be
noted later, lactose, so commonly regarded as a sugar unique to the
female mammal, is also to be found in the vegetable kingdom. Fourthly,
we have the two widely distributed nonreducing disaccharides sucrose
(G/\/Ff) and trehalose (G\/\/G) which seem to be forms in which
potential energy can be transported or stored in a readily available form
in the sap or body fluids of many organisms. In addition, it has become
clear that sucrose molecules, and possiblv trehalose as well, form
"anchors" on to which may be attached considerable numbers of other
sugar units, usually in chains, to generate higher oligo- and polysaccharides. The fructosans of the inulin and levan types can often be shown
directly or indirectly to contain a moiety having the sucrose structure
(see Chapter 8).
The nonreducing disaccharides and their homologs will be considered first.
A. NONREDUCING OLIGOSACCHARIDES
1. aa-Trehalose
This sugar (XCII) has been known for a very long time; it was
first obtained from ergot in 1832 (204) but got its name from trehala
manna (of insect origin) from which it was isolated in 1859 (205). A
full historical account of early work on trehalose has been published
(206). The sugar occurs in a wide variety of situations, in fungi, freshwater algae, lichens, a pteridophyte (Selaginella lepidophylh), yeasts,